Echography is a technology which uses sound waves. With this technology, organs or an unborn child, inter alia, can be visualised. Applications also exist outside medical science.
Sound waves are transmitted into the body of a human or animal using a transducer. The sound waves reflected by the body are picked up on return by the same transducer and converted into an electrical voltage. The electrical signals are converted using a computer system into video images, which are visualised on a monitor of the echoscope.
In a plurality of applications in which an echoscope is used, the localisation of a needle is important. This applies in the case of the piercing of blood vessels, the guiding of a puncture needle in the case of, for example, amniotic fluid punctures or biopsies, in the insertion of catheters for ablation, for drainage, access to blood vessels, anaesthesia such as, for example, a local anaesthetic wherein a plexus is surrounded by anaesthesia via a puncture, etc. All manner of treatments wherein a body is pierced with needles such as occupational therapy, microwaves and radio frequency can also use echography with localisation.
A needle of this type is often inserted with a free hand, wherein the zone to be pierced is visualised using the echoscope and a check is carried out during the piercing to ensure that the needle is correctly inserted. However, the insertion of a needle with the free hand requires a certain dexterity and experience in order to insert the needle with reasonable accuracy. Only if the needle has actually pierced will it appear or not appear in the image of the zone visualised using the transducer and the echoscope. If it is established that the needle is not in the area of the echoscope or near the zone to be pierced, the piercing must often be repeated several times. However, more than one piercing causes discomfort to the patient and additional piercing damage, and may, in the case of the piercing of tumours, even be fatal.
To overcome this problem, needle guides have been developed with which the needles are guided so that it is certain that the needle is inserted into the area which is visualised with the echoscope and the transducer. A needle guide of this type is positioned on a holder which is fitted to the transducer. With the first needle guides, however, only a needle with a specific diameter could be inserted at a specific angle into the body.
Systems with needle guides already exist, wherein the angle at which a needle is inserted into a body can be determined step-by-step, according to the area which is visualised. In needle guides of this type, the needle can be brought at different predefined angles into the area visualised with the echoscope. It is already possible to visualise these predefined angles on the monitor of the echoscope. By positioning the transducer, wherein the zone of the body to be pierced is visualised, wherein the different possible angles for piercing are also visualised, the angle for piercing which produces the best result can be selected. However, this system still has a limited accuracy, so that the desired result is often not immediately achieved with the piercing, which must then be repeated several times. As already mentioned, more than one piercing causes discomfort to the patient and additional piercing damage, and may, in the case of the piercing of tumours, even be fatal.
Systems already exist wherein the needle can be displaced in a stepless manner in an area using the needle guide, and the position of the needle can nevertheless be accurately determined. These systems use magnetic localisation, known as GPS systems. A clamp, to which the guide is fitted, is positioned on the transducer. Accurate localisation of the needle is possible with a magnet and a plurality of sensors. One sensor is positioned on the clamp, another on or in an ancillary needle or on a standard sterile needle. The angle at which the ancillary needle or the standard sterile needle is inserted into the body can be determined using the sensors. The predicted angle at which the ancillary needle enters the body is displayed on the monitor. However, the use of an ancillary needle has the disadvantage that the ancillary needle has a larger diameter than the actual needle with which the treatment is to be carried out, so that the actual needle (possibly following removal of the sensor, if this had been inserted into the ancillary needle) can be inserted through the ancillary needle into the body. The use of ancillary needles is furthermore expensive. Both in the case of the use of an ancillary needle and in the case of systems wherein a sensor is attachable directly to a standard sterile needle, the magnet and associated sensors for a magnetic location determination of this type are fairly expensive. If the sensor is positioned on or in the needle, this must also be sterile. In these systems, a new sterile sensor and (if ancillary needles are used) a new sterile ancillary needle are normally used for each treatment. In this way, a treatment costs a lot of money. If ancillary needles with larger diameters are used, much more damage is furthermore caused than if only the actual needles with the necessary diameter are applied.